Circular breathing is an essential part of oboe technique. Everyone who has learned the technique will never give it up. However, circular breathing is regarded with suspicion by some, who regard it as a virtuoso party trick that distorts the natural human qualities of music. So, it is important not to use it in that way. Circular breathing is not really intended to increase the distance between breathing points. Rather, it is a wonderful technique that can enhance playing and increase comfort. Increased comfort gives increased endurance, more stability, better tone quality, and less tension.

There are two elements to the technique. You must be able to "spit" air through the reed rather than blowing. And, you must be able to breathe in and out through your nose while spitting the air in your mouth.

First, we get comfortable spitting...
1. Take a mouthful of water, and spit it into the sink through a coffee straw. The coffee straw approximates the resistance of the oboe. You'll probably have to puff your cheeks a fair amount. Observe that a forward movement of the tongue also propels the water. Since the oboe doesn't need much quantity of air, that tongue motion is what will eventually push all of the air through the reed. The cheek puffing will not be necessary, and should be regarded as a preparatory exercise only. We are beginning with water rather than air for a reason: oboe players are so used to blowing air that they are initially unable to distinguish between blowing and spitting if only air is involved. But, if we use water instead of air, the difference will be very clear.
2. Try the same thing with air. Take the coffee straw, submerge it in a glass of water, and see how long you can keep the air bubbles going. Remember not to blow air, spit air.
3. Try the same thing with a reed. You should be able to sustain a sound for about 2-3 seconds. The sound needs to have good energy and intensity, and be around a "C" in pitch (two octaves above middle C on the piano).
4. And, try it with the oboe. Adding the oboe to the equation adds some more resistance to the picture, but again you should be able to sustain a sound for 2-3 seconds just spitting. Try to use mostly (or entirely) the tongue to push the air through the reed.

Once you're comfortable spitting, practice breathing in and out while doing it. Don't worry about playing music just yet. Spit air through the reed (or the coffee straw) and breathe in and out while you do it. You may want to back up to step 1 above if the oboe's resistance is too distracting. Then, back to the reed and eventually to the oboe.

Now comes the tricky part. You want to transition from blowing to spitting to blowing again. Take your time. Most beginners feel like they have to do this all in a big rush and take the breath in a split second. You don't. If you can make a sound for 2-3 seconds while spitting, that gives you a lot of time to take your breath. Relax.

There will always be a small bump in the sound as you make the transitions. At first, there may be a large bump or even no sound at all. Relax, take your time, and do everything smoothly. Then, after you can do it, pick your spots carefully. Trills and fast scales are great places to circular breathe. Soft long notes are bad. Some things are very difficult to do while circular breathing. Tonguing, for example, is possible but awkward and best avoided. I have never figured out how to create a vibrato while circular breathing, so expressive passages are not good candidates.

Now, you can enjoy your newfound freedom. For example, the first long statement of the Strauss Concerto has several easy and logical places to breathe. Use these to exhale only, and use circular breathing to inhale while playing the sixteenth notes. It makes the opening statement almost easy from a physical perspective, and allows you to actually play fortissimo at the end and think about shaping and pacing the music.